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141.
In the recent past, suspended zipper‐braced frames were proposed to avoid one‐storey collapse mechanisms and dynamic instability under severe ground motions. In this paper, the design procedure suggested by Yang et al. is first slightly modified to conform to the design approach and capacity design rules stipulated in Eurocode 8 for concentrically braced frames. The procedure is applied to a set of suspended zipper‐braced frames with different number of storeys and founded on either soft or rock soil. The structural response of these frames is analysed to highlight qualities and deficiencies and to assess the critics reported by other researchers with regard to the design procedure by Yang et al. Then, improvements are proposed to this procedure to enhance the energy dissipation of the chevron braces and the response of the structural system as well. The effectiveness of the design proposals is evaluated by incremental dynamic analysis on structures with different geometric properties, gravity loads and soil of foundation. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
142.
A multi‐level seismic vulnerability assessment of reinforced concrete moment frame buildings located in moderate seismic zones (0.25g) is performed on a set of ductile versions of low‐ to mid‐rise two‐dimensional moment frames. The study is illustrated through application to comparative trial designs of two (4‐ and 8‐story) buildings adopting both space‐ and perimeter‐framed approaches. All frames are dimensioned as per the emerging version of the seismic design code in Egypt. These new seismic provisions are in line with current European norms for seismic design of buildings. Code‐compliant designs (CCD), as well as a proposed modified code design relaxing design drift demands for the investigated buildings, are examined to test their effectiveness and reliability. Applying nonlinear inelastic incremental dynamic analyses, fragility curves (FC) for the frames are developed corresponding to various code‐specified performance levels. Code preset lower and upper bounds on design acceleration and drift, respectively, are also addressed along with their implications, if imposed, on the frames seismic performance and vulnerability. Annual spectral acceleration hazard curves for the case study frames are also generated. Estimates for mean annual frequency (MAF) of exceeding various performance levels are then computed through an integration process of the data resulting from the FC with the site hazard curves. The study demonstrates that the proposed design procedure relaxing design drift demands delivers more economic building designs relative to CCDs, yet without risking the global safety of the structure. The relaxed design technique suggested herein, even though scoring higher, as expected by intuition, MAF of exceeding various code‐limiting performance levels expressed in terms of interstory drift ratios, still guarantees a reasonably acceptable actual margin against violating code limits for such levels. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
143.
Maria Teresa Giugliano Alessandra Longo Rosario Montuori Vincenzo Piluso 《地震工程与结构动力学》2011,40(13):1455-1474
Structural engineering problems are always affected by many sources of uncertainty, such as aleatory of material properties, applied loads and earthquake intensity, therefore, seismic assessment of structures should be based on probabilistic methods. Since PBSD (Performance‐based Seismic Design) philosophy was formulated, many researches have been conducted in this field in order to develop simple and accurate procedures for evaluating structural reliability. An important contribution has been provided by Jalayer and Cornell, who have developed a closed‐form expression to evaluate the mean annual frequency of exceeding a defined limit state. In this paper, by assuming the record‐to‐record variability as the only source of uncertainty, the seismic reliability of concentrically braced frames designed according to traditional and innovative methodologies is investigated, and a comparison between their performances is presented. In particular, two design methodologies have been applied: Eurocode 8 provisions and a new design methodology based on a rigorous application of ‘capacity design’ criteria. The innovative reduced section solution strategy, based on the reduction of cross sections at bracing member ends, has also been analysed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
144.
底层带支撑异型柱框架非线性地震反应分析 总被引：2，自引：2，他引：0
本文利用ＤＲＡＩＮ－２Ｄ程序对底层带支撑异型柱框架进行了时程分析,并且与无支撑异型柱框架及通高设支撑异型柱框架进行了比较分析,结果表明,笔者提出的底层带支撑异型柱框架是一种良好的结构形式。 相似文献
145.
Buckling restrained braces (BRBs) are very effective in dissipating energy through stable tension–compression hysteretic cycles and have been successfully experimented in the seismic protection of buildings. Their behavior has been studied extensively in the last decades and today the level of performance guaranteed by these devices and the technological constrains that have to be fulfilled to optimize their behavior are well known. Furthermore, several companies in the world have developed their own BRBs and are now producing them. In spite of this, many seismic codes (for instance, the EuroCode 8) do not stipulate provisions for the design and construction of earthquake‐resistant structures equipped with BRBs. This discourages the structural engineering community from using these devices and seriously limits their use in structural applications. In this paper a procedure for the seismic design of steel frames equipped with BRBs is proposed. Furthermore, the paper presents a numerical investigation aimed at validating this design procedure and proposing the value of the behavior factor q that should be used for this structural type. To this end, a set of frames with BRBs is first designed by means of several values of q. Then, the obtained frames are subjected to a set of accelerograms compatible with the elastic response spectrum considered in design. The seismic response of the frames is determined by nonlinear dynamic analysis and represented in terms of the ductility demand of BRBs and the internal force demand of nondissipative members (beams and columns). Finally, the largest value of q that leads to acceptable seismic performance of the analyzed frames is assumed as adequate. The value of q is given in the paper as a continuous function of the assumed ductility capacity of the BRBs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
146.
In this paper, a technique is presented which employs the results of pseudo‐dynamic tests for the development of a mathematical model. This technique, described by means of the mathematical modelling of a three‐storey reinforced concrete frame building with infill in the bottom two storeys, which was tested at ELSA in Ispra, proved to be effective and to lead to a fairly accurate structural model. The results of analyses suggest that the global non‐linear seismic response of reinforced concrete frames with masonry infill can be adequately simulated by a relatively simple mathematical model, which combines beam elements with concentrated plasticity, simple connection elements, and equivalent strut elements representing the infill walls (provided that the infill does not fail out of plane and that no shear sliding failure occurs). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
147.
H. U?ur Koyliioglu Ahmet ?. Çakmak Søren R.K. Nielsen 《Soil Dynamics and Earthquake Engineering》1997,16(2):95-112
A nonlinear hysteretic model for the response and local damage analyses of reinforced concrete shear frames subject to earthquake excitation is proposed, and, the model is applied to analyse midbroken reinforced concrete (RC) structures due to earthquake loads. Each storey of the shear frame is represented by a Clough and Johnston hysteretic oscillator with degrading elastic fraction of the restoring force. The local damage is numerically quantified in the domain [0,1] using the maximum softening damage indicators which are defined in closed form based on the variation of the eigenfrequency of the local oscillators due to the local stiffness and strength deterioration. The proposed method of response and damage analyses is illustrated using a sample 5 storey shear frame with a weak third storey in stiffness and/or strength subject to sinusoidal and simulated earthquake excitations for which the horizontal component of the ground motion is modeled as a stationary Gaussian stochastic process with Kanai-Tajimi spectrum, multiplied by an envelope function. 相似文献
148.
Swaminathan Krishnan 《地震工程与结构动力学》2007,36(7):861-885
This paper describes the three‐dimensional nonlinear analysis of six 19‐storey steel moment‐frame buildings, designed per the 1997 Uniform Building Code, under strong ground motion records from near‐source earthquakes with magnitudes in the range of 6.7–7.3. Three of these buildings possess a reentrant corner irregularity, while the remaining three possess a torsional plan irregularity. The records create drift demands of the order of 0.05 and plastic rotation demands of the order of 4–5% of a radian in the buildings with reentrant corners. These values point to performance at or near ‘Collapse Prevention’. Twisting in the torsionally sensitive buildings causes the plastic rotations on the moment frame on one face of the building (4–5% of a radian) to be as high as twice of that on the opposite face (2–3% of a radian). The asymmetric yield pattern implies a lower redundancy in the lateral force‐resisting system as the failure of the heavily loaded frame could result in a total loss of resistance to torsion. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
149.
Brittle fractures occurring at the beam–column connections of welded steel moment frames, such as those observed following the Mw 6.7 1994 Northridge earthquake, result in sudden decreases in connection strength and stiffness. These changes lead to various types of transient dynamic behavior at the local and global levels. The effects on global acceleration include highly transient, high‐frequency waveforms that occur immediately following fracture and decay quickly. The theoretical basis for the occurrence of these transient waveforms is examined and their presence in structural analysis results is demonstrated. Results from shaking table experiments on a simple steel moment frame with fracturing connections show that transient accelerations are consistently observed following fracture. These experiments and analyses show that, due to their short duration, the transient acceleration waveforms do not cause any sudden changes in the global lateral displacement response of typical building structures. Therefore, these global acceleration transients have relatively benign effects on overall system behavior despite their relatively large amplitudes. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
150.
The paper presents the results of an investigation into the dispersion values, expressed in terms of limit‐state spectral accelerations, which could be used for the pushover‐based risk assessment of low‐height to mid‐height reinforced concrete frames and cantilever walls. The results of an extensive parametric study of a portfolio of test structures indicated that the dispersion values due to record‐to‐record variability and modelling uncertainty (βLS,RU) are within the range from 0.3 to 0.55 for the near collapse limit state, and between 0.35 and 0.60 for the collapse limit state. The dispersions βLS,RU proposed for the code‐conforming and the majority of old (non code‐conforming) frames are in between these values. On the other hand, the dispersions proposed for the old frames with a soft storey and an invariant plastic mechanism, and for the code‐conforming cantilever walls, are at the lower and upper bounds of the presented values, respectively. The structural parameters that influence these dispersions were identified, and the influence of different ground motion sets, and of the models used for the calculation of the rotation capacities of the columns, on the calculated fragility parameters was examined and quantified. The proposed dispersion values were employed in a practice‐oriented pushover‐based method for the estimation of failure probability for eight selected examples. The pushover‐based risk assessment method, although extremely simple and economical when compared with more rigorous probabilistic methods, was able to predict seismic risk with reasonable accuracy, thus showing it to be a practical tool for engineers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献